Can a Lizard Break off Its Tail?
Have you ever seen an animal drop off its tail? Grass snakes and certain other lizards can leave their tails behind to save their lives. Most lizards have tails longer than their bodies. If an enemy catches the lizard by the tail, the lizard quickly breaks off its tail, which continues to wiggle for a few minutes.
While the twitching tail holds the attention of the would-be attacker, the lizard makes a safe getaway. The lizard does not seem to miss its tail, and it soon grows a new one to replace it. But the new tail is never as long as the original one.
The technical term for this ability to drop the tail is caudal autotomy. In most lizards that sacrifice the tail in this manner, breakage occurs only when the tail is grasped with sufficient force, but some animals, such as some species of geckos, can perform true autotomy, throwing off the tail when sufficiently stressed, such as when attacked by ants.
Some such lizards, in which the tail is a major storage organ for accumulating reserves, will return to a dropped tail after the threat has passed, and will eat it to recover part of the sacrificed supplies. Conversely, some species have been observed to attack rivals and grab their tails, which they eat after their opponents flee.
Caudal autotomy in lizards takes two forms. In the first form, called intervertebral autotomy, the tail breaks between the vertebrae. The second form of caudal autotomy is intravertebral autotomy, in which there are zones of weakness, fracture planes across each vertebra in the mid-part of the tail.
In this second type of autotomy the lizard contracts a muscle to fracture a vertebra, rather than break the tail between two vertebrae. Sphincter muscles in the tail then contract around the caudal artery to minimize bleeding.